Bronchopulmonary complications

Complications in viral infections (using influenza as an example)

In influenza, respiratory system involvement depends on the severity of the course and the accession of a secondary infection. The virus directly damages type I pneumocytes, destroying the air-blood barrier, as well as type II pneumocytes, reducing surfactant production. This leads to interstitial edema and acute respiratory failure.

• Moderate course: Characterized by serous-hemorrhagic inflammation. Desquamated epithelium and thick mucus form plugs that occlude small bronchi. Atelectasis and perifocal emphysema develop. It may resolve into focal or interstitial pneumonia.
• Severe toxic variant: Hemorrhagic and necrotic components dominate due to the pronounced vasopathic properties of the virus. Hemorrhagic pulmonary edema occurs. In children, laryngeal mucosal edema with luminal stenosis (false croup) may develop.
• Influenza with bacterial complications: Occurs approximately a week after onset. Severe focal-confluent purulent bronchopneumonia forms with areas of lung tissue destruction (segmental destructive panbronchitis).

Macroscopically, the lung in secondary bacterial infection is sharply enlarged and has a characteristic "large variegated lung" appearance due to the alternation of red-gray protruding inflammatory foci, bluish atelectasis, light-gray bloated areas of emphysema, dirty-gray abscesses, and dark-red hemorrhages.

Respiratory system involvement in cystic fibrosis

Bronchopulmonary disorders in cystic fibrosis develop as a consequence of hypersecretion of ultra-viscous mucus. The predominantly pulmonary form occurs in 15–20% of patients, while the mixed form (with gastrointestinal involvement) occurs in 78–80% of cases. Respiratory syndrome eventually comes to the foreground: persistent cough, dyspnea, and bronchorrhea appear.

Thick sputum creates ideal conditions for secondary infection to join. A progressive purulent-inflammatory process forms, leading to structural remodeling of the lungs:

1. Development of diffuse pneumofibrosis and pneumosclerosis.
2. Formation of bronchiectasis, cysts, and atelectasis.
3. Development of pulmonary emphysema.

Chronic hypoxia leads to specific deformation of the terminal phalanges of the fingers ("clubbing"), and the chest acquires a deformed appearance. The hemodynamic outcome of these changes is pulmonary hypertension with the formation of cor pulmonale and right ventricular failure. Life-threatening conditions include pneumothorax, pyopneumothorax, as well as hemoptysis and massive pulmonary hemorrhage.

Neonatal aspiration syndromes

In newborns, bronchopulmonary complications are often associated with aspiration of pathological contents:

• Meconium aspiration syndrome: Occurs against the background of intrauterine asphyxia or stress, which causes the release of meconium into the amniotic fluid. Viscous masses obstruct the airways, causing severe inflammation and respiratory distress syndrome (RDS). Radiographs show large irregular shadows mixed with areas of increased transparency (emphysema) and flattening of the diaphragmatic dome.
• Milk aspiration: Typical for premature infants due to immaturity of the neuromuscular apparatus (swallowing discoordination). It manifests as obstruction, episodes of apnea, and cyanosis. It requires positional therapy (feeding on the right side), and in case of persistent symptoms, the exclusion of congenital anomalies such as esophageal atresia or tracheoesophageal fistula.

Bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a chronic lesion of the lung tissue that occurs in premature newborns who have suffered from RDS. The pathology is a consequence of intensive care.

The pathogenesis is based on several damaging factors:

• Mechanical impact: barotrauma during mechanical ventilation.
• Oxygen toxicity: high concentrations of the breathing mixture cause oxidative stress (free radical damage) and paralyze the function of the ciliated epithelium.
• Surfactant deficiency: leads to alveolar instability, their collapse, and uneven ventilation.

As a result, pronounced edema and structural damage to the lung parenchyma are formed, requiring prolonged respiratory support.

Class and exam questions

What else to study on this topic

• Morphological markers of uncomplicated influenza (basophilic and eosinophilic inclusions in the epithelium)
• Extrapulmonary manifestations of severe influenza: Waterhouse–Friderichsen syndrome and CNS lesions
• Gastrointestinal manifestations of cystic fibrosis (meconium ileus, pancreatic insufficiency)
• Diagnostic algorithms for cystic fibrosis (sweat test and molecular genetic DNA testing)
• Differential diagnosis of aspiration syndrome with congenital anatomical anomalies (tracheoesophageal fistula)

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.